Dual polarized antenna system with controlled field pattern

ABSTRACT

A DIRECTIONAL ANTENNA SYSTEM PROVIDES BOTH VERTICAL AND HORIZONTAL POLARIZATION. A SPIRE NEAR THE TOP OF A SKYSCRAPER CARRIES A PAIR OF VERTICALLY ORIENTED DIPOLES ON OPPOSITE CORNERS. A POWER DIVIDER DELIVERS MORE ENERGY TO ONE OF THE DIPHOLES THAN TO THE OTHER. THE SPIRE ALSO CARRIES A SLOTTED RING ANTENNA HAVING FED DIRECTIONALIZING ELEMENTS AND COEXTENSIVE WITH AN EXTENSION OF ONE OF THE DIPOLES TO PROVIDE SUBSTANTIALLY THE SAME HORIZONTAL DIRECTIONALITY PATTERN FOR HORIZONTALLY POLARIZED ENERGY AS THE VERTICALLY ORIENTED DIPOLES PROVIDE FOR VERTICALLY POLARIZED ENERGY.

I Jan. 12, 1971 A. ALFO RD DUAL POLARIZED ANTENNA SYSTEM WITH CONTROLLED FIELD PATTERN Filed Dec. 19, 1969 4 Sheets-Sheet 1 YNVENTOR. ANDREW ALFORD MMYM ATTORNEYS Jan. A. ALFORD DUAL POLARIZED ANTENNA SYSTEM WITH CONTROLLED FIELD PATTERN Fined Dec. .19. 1969 4 Sheets-Sheet 2 HIGH LEVEL LOW LEVEL OUTPUT OUTPUT 5 s 0 5; 4x2 LI IN 4 COVER 46 SHORT CIRCUIT I I0 l WTFM +4 W T INPUT [.00

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FREQUE NCY MC VSWR INVENTOR. G 4 ANDREW ALFORD ATTORNEYS Hlwm I Jan 12,- 1971 I A. ALF'ORD 3,555,552

DUAL POLARIZED ANTENNA SYSTEM ITH CONTROLLED FIELD PATTERN Filed Dec. 19, 1969- 4 Sheets-Sheet 5 FIG.5

INVENTOR. ANDREW ALFORD ATTORNEYS Jm. 1 2,1911 Amman v 3,555,552

DUAL POLARIZED ANTENNA SYSTEM WITH CONTROLLED FIELD PATTERN Filed Dec. 19, 1969 4 Sheets-Sheet 4 INVENTOR ANDREW ALFORD ATTORNEY United States Patent O F 3,555,552 DUAL POLARIZED ANTENNA SYSTEM WITH CONTROLLED FIELD PATTERN Andrew Alford, 120 Cross St., Winchester, Mass. 01890 Continuation-impart of application Ser. No. 590,049,

Oct. 27, 1966. This application Dec. 19, 1969, Ser.

Int. Cl. H01q 21/00 US. Cl. 343-726 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This application is a continuation-in-part of application Ser. No. 590,049, filed Oct. 27, 1966, now abandoned.

The present invention relates in general to electromagnetic transduction and more particularly concerns a novel antenna system that coacts with the structure upon which it is mounted to provide desired directional characteristics. An actual commercial embodiment of the invention provides both horizontal and vertical polarization having substantially the same radiation characteristic in the horizontal plane.

SUMMARY OF THE INVENTION According to the invention there is a vertical mounting means which may be a spire near the top of a skyscraper. First and second vertically oriented dipoles are supported from the vertical mounting means separated by the mounting means and in a plane that also embraces the axis of the mounting means. Means defining an input line is coupled to the first and second vertical dipoles by power dividing means that couple much more energy between said input transmission line means and said first dipole than between said input transmission line means and said second dipole, the spacing of said dipoles relative to each other and said mounting means coacting to provide two angularly spaced nulls in the horizontal radiation pattern on opposite sides of said plane while providing a relatively wide maximum of radiation through a horizontal angle of nearly 180 degrees which horizontal angle embraces said plane.

According to another aspect of the invention there is a slotted ring antenna substantially coextensive with an extension of the first vertical dipole and fed directionalizing elements that coact with said support means and said slotted ring antenna to provide substantially the same horizontal directionality pattern for horizontally polarized energy as the above-described apparatus provides for vertically polarized energy.

In the early stages of frequency modulation broadcasting most antennas were characterized by horizontal polarization and omnidirectionality in the horizontal plane. Later, directional antennas were employed in order to facilitate serving the maximum listening area 3,555,552 Patented Jan. 12, 1971 "ice while minimizing interference with other services. The increase in automobile F-M receivers, which usually have vertical receiving antennas, made it desirable to also radiate vertically polarized energy. The numerous listeners having horizontally polarized receiving antennas made it impractical to abandon horizontal polarization.

It is an important object of this invention to provide electromagnetic transducing apparatus characterized by substantially uniform radiation over a relatively large but limited angle in the horizontal plane.

It is a further object of the invention to achieve the preceding object with vertically polarized energy.

It is another object of the invention to achieve the first object with horizontally polarized energy.

It is still another object of the invention to achieve the preceding objects whereby the horizontal radiation pattern for both vertical and horizontal polarization are substantially the same.

It is still another object of the invention to achieve the preceding objects while establishing nulls in prescribed directions.

Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 and 5 are perspective views of a system according to the invention mounted on the spire of the Chrysler Building in New York City;

FIG. 2 is the horizontal radiation pattern of the antenna system;

FIG. 3 is a diagrammatic representation of the power dividing means for feeding the two vertically polarized dipoles;

FIG. 4 is the VSWR as a function of frequency of the antenna system according to the invention actually installed on the Chrysler Building; and

FIG. 6 is a top view of the horizontally polarized slotted ring antenna on the Chrysler Building through section 5-5 of FIG. 5.

With reference now to the drawing and more particularly FIGS. -1 and 5 thereof, there is shown an antenna installation according to the invention mounted upon the spire of the Chrysler Building providing both horizontal and vertical polarization with the radiation characteristic of FIG. 2 in the horizontal plane. The horizontally polarized antenna comprises a slotted ring antenna of the type disclosed in Alford Pat. No. 2,611,867 and 2,622,196 and corresponding to a commercially available Alford Type 1049 antenna element 11 mounted on the east by north corner 12 of the spire 13 and coacting with the spire 13 and the fed directionalizing elements 14 and 15 to establish the radiation pattern in the horizontal plane shown in FIG. 2. The slotted ring assembly lower point 16 and upper point 17 each branch out into first and second directionalizing element support lines 21 and 22 for supporting the directionalizing elements 14 and 15. Directionalizing elements 14 and 15 each comprise a conducting link formed as shown, such as 23 and 24, respectively, supported by line 22 and similar elements 25 and 26, respectively, supported by line 21. Directionalizing element 14 is located just above lower intermediate ring 27 and directionalizing element 15 is located just above upper intermediate ring 28. A horizontally polarized input feed line 31 receives energy from the transmitter for radiation with horizontal polarization for coupling to rigid coaxial line 30 that makes a right angle bend along central ring 29.

The dipole elements 32 and 33 coact with the spire to provide vertically polarized energy with the directional characteristic of FIG. 2 in the horizontal plane together with power dividing means that furnishes much more power to element 32 than to element 33, a typical division being 99 percent to element 32 and 1 percent to element 33. Elements 32 and 33 comprise two commercially available Alford Type 7472 dipoles. A first rigid coaxial line 34 feeds dipole 32 and a second rigid coaxial line 35 feeds dipole 33, these two lines being fed from a power divider schematically represented in FIG. 3.

With reference to FIG. 3, there is shown a diagrammatic representation of the power dividing means. This is preferably a coaxial line network as shown having an input branch 36 energized by the transmitter for receiving energy to be radiated with vertical polarization, a high level output branch 37 for coupling to transmission line 34, a low level output branch 41 for coupling to transmission line 35, an intercoupling section 42 and a short circuiting stub section 43 for adjusting the dis tribution of power between low level output branch 41 and high level output branch 37. Short circuiting branch 43 includes an adjustable sliding short circuit 44 adjusted by a handle 45 enclosed by cover 46 when adjustment is complete. The closer sliding short circuit 44 is to low level output branch 41, the less power delivered to low level output branch 41.

Referring to FIG. 4, there is shown the input VSWR of the directional antenna actually installed on the Chrysler Building as measured at the input of the coaxial switch in the transmitter area. In the specific installation on the Chrysler Building where the diagonal passing through the corners on which dipoles 32 and 33 are mounted corresponds to a line of direction of 74 degrees azimuth, it was found advantageous to rotate antenna element 11 about an axis through feed points 16 and 17 five degrees east so that a diameter passing through this vertical axis was coextensive with the 79 degree azimuth radial. It was also found advantageous to rotate dipoles 32 and 33 12 degrees east so that the plane of each of these dipoles was coextensive with the azimuth radial of substantially 86 degrees, thereby providing the desired radiation pattern symmetrical about the easterly direction of substantially 90 degrees azimuth.

Preferably the directionalizing members 14 and 15 and the associated supports comprise extruded thick walled aluminum tubes approximately one inch in outer diameter with a inch inner diameter having a heating wire supported by continuous ceramic insulation. The heating wire is fed by a hermetically sealed transformer to afford deicing. The dipoles 32 and 33 were each constructed primarily from a rugged aluminum casting closed with removable aluminum covers on one side to provide a means for installing internal deicers.

The magnitude of the problems solved by the invention will be appreciated from a recognition of the specific requirements that had to be met. The effective radiated power in the direction of an F-M station in Newton, NJ. had to be restricted to 270 watts and that in the direction of a Princeton, NJ. station 2360 watts While complying with the FCC rules which limit the change in radiation on either side of each null to a maximum of 2 db for every degree change in azimuth. Still an additional problem presented was that the Chrysler Building is symmetrical about a 74 degree azimuth while the specified horizontal radiation pattern is approximately symmetrical about a 90 degree azimuth (due east).

Referring to FIG. 6, there is shown a view through section 55 helpful in understanding the shape and position of elements 14 and relative to the spire 13 and the manner of feeding. Only element 14 is shown in FIG. 6; however, the plan view of element 15 is identical. The slotted ring antenna comprises a slot 41 defined by gaps across each of the rings, such as center ring 29, the edges of one side of the gap being interconnected by rod 42 and on the other by rod 43. The slot is fed across center ring 29 by connecting the outer conductor of line 30 to edge 44 of ring 29 and the inner conductor to opposed edge 45. Alford US. Pat. No. 2,798,217 describes a slotted ring antenna and Alford US. Pat. No. 2,611,867 describes in FIG. 6d whisked-like directionalizing elements across a slot in a cyilndrical antenna for providing a directionalizing effect.

It is to be understood that the principles of this invention are applicable to both transmitting and receiving. It is also to be understood that either the horizontally polarized subcombination or the vertically polarized subcombination may be used separately within the principles of the invention. Numerous other uses and modifications of and departures from the specific embodiment described herein may now be practiced by those skilled in the art without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and construed as limited solely by the spirit and scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

I claim:

1. Electromagnetic transduction apparatus comprising,

mounting means,

first and second dipole means oriented with dipole arms substantially parallel to and in the axial plane embracing the axis of said mounting means,

said first and second dipole means being separated by said mounting means,

means defining in input line,

means including power dividing means coupling said input line to said first and second dipole means for exchanging much more energy between said input line and said first dipole means than between said input line and said second dipole means,

the spacing of said dipole means relative to each other and said first and second dipole means and said mounting means coacting to provide for energy polarized parallel to said axial plane having two angularly spaced nulls in a first radiation pattern in a normal plane substantially perpendicular to said mounting meansaxis which nulls are separated by said axial plane axis while providing a relatively wide maximum of radiation through an angle in said normal plane which angle embraces said axial plane,

a slotted ring antenna substantially coextensive with an extension of the dipole arms of said first dipole means, and

fed directionalizing element means for coacting with said mounting means and said slotted ring antenna to provide a second radiation pattern in said normal plane corresponding substantially to said first radiation pattern for energy polarized parallel to said normal plane,

said slotted ring antenna and said first and second dipole means 'being operative over substantially the same frequency range.

2. Electromagnetic transduction apparatus in accordance with claim 1 wherein said power dividing means includes means for establishing the energy division between said first and second dipole means in the ratio of substantially :1.

3. Electromagnetic transduction apparatus in accordance with claim 1 wherein said slotted ring antenna comprises a plurality of stacked rings fed from a first feedline, and

said fed directionalizing element means comprises supporting rods branching from the extremities of said slotted antenna and having an intermediate portion generally parallel to the axis of said stacked rings 5 and substantially tangential to said stacked rings References Cited substantially along a line diametrically opposed to UNITED STATES 1P ATENTS said first feedline, and a plurality of pairs of directionalizing rods extending 2510290 6/1950 Masters 343 727 from said supporting rods with each pair partially surrounding the volume defined by said stacked 5 ELI LIEBERMAN Pnmary Examiner rings and defining a plane substantially perpendicu- US. Cl. X.R.

lar to the axis of said stacked rings. 343--89O 

